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NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models.

Hsu LT, Gu Y, Kamijo S - Sensors (Basel) (2015)

Bottom Line: The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange.Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal.According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. qmohsu@kmj.iis.u-tokyo.ac.jp.

ABSTRACT
Currently, global navigation satellite system (GNSS) receivers can provide accurate and reliable positioning service in open-field areas. However, their performance in the downtown areas of cities is still affected by the multipath and none-line-of-sight (NLOS) receptions. This paper proposes a new positioning method using 3D building models and the receiver autonomous integrity monitoring (RAIM) satellite selection method to achieve satisfactory positioning performance in urban area. The 3D building model uses a ray-tracing technique to simulate the line-of-sight (LOS) and NLOS signal travel distance, which is well-known as pseudorange, between the satellite and receiver. The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange. The measurement of the satellite will be excluded if the simulated and raw pseudoranges are inconsistent. Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal. According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

No MeSH data available.


Flowchart of the particle filter using 3D city building models and receiver autonomous integrity monitoring (RAIM) multiple fault detection and exclusion (FDE).
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sensors-15-17329-f004: Flowchart of the particle filter using 3D city building models and receiver autonomous integrity monitoring (RAIM) multiple fault detection and exclusion (FDE).

Mentions: The idea of RAIM FDE is to exclude the satellite with larger pseudorange residual. As mentioned earlier, it is capable of excluding abnormal signals. An illustration of the devastated effect of the particle filter is depicted in Figure 3. This paper therefore proposes the idea of RAIM to overcome the drawback. Figure 4 shows the flowchart of the use of the proposed RAIM FDE in the 3D map method. The red-frame of Figure 4 is the newly proposed method in this paper. As shown in Figure 4, the RAIM FDE will be used after calculating the simulated pseudorange of a candidate. It is interesting to note the idea of the pseudorange difference of each candidate in the proposed 3D map positioning method is similar to the pseudorange residual of the RAIM algorithm. In the proposed method, the pseudorange difference is defined as the pseudorange measurement minus the simulated pseudorange. The simulated pseudorange is calculated as:(1)ρ^n(i)=Rn(i)+c(δtr(i)−δtnsv)+In+Tn+εnrefl(i)where n denotes the index of the satellite, i denotes the index of a position candidate (particle), denotes geometric distance between the satellite n and the candidate i, c denotes the speed of light, the satellite clock and orbit offset are corrected using the satellite broadcast model. The ionospheric delay I and the tropospheric delay T are obtained from the Klobuchar and Saastamoinen models, respectively. The reflection delay is estimated by the ray tracing and city building models [23,24,25]. The receiver clock offset, , for the candidate is modified to minimize the difference between the simulated set and the measured set. If an abnormal signal is used in the calculation of the receiver clock bias minimization, the optimized receiver clock bias will be inaccurate. The flowchart of the RAIM multiple fault exclusion in the proposed method is shown in Figure 5.


NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models.

Hsu LT, Gu Y, Kamijo S - Sensors (Basel) (2015)

Flowchart of the particle filter using 3D city building models and receiver autonomous integrity monitoring (RAIM) multiple fault detection and exclusion (FDE).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541937&req=5

sensors-15-17329-f004: Flowchart of the particle filter using 3D city building models and receiver autonomous integrity monitoring (RAIM) multiple fault detection and exclusion (FDE).
Mentions: The idea of RAIM FDE is to exclude the satellite with larger pseudorange residual. As mentioned earlier, it is capable of excluding abnormal signals. An illustration of the devastated effect of the particle filter is depicted in Figure 3. This paper therefore proposes the idea of RAIM to overcome the drawback. Figure 4 shows the flowchart of the use of the proposed RAIM FDE in the 3D map method. The red-frame of Figure 4 is the newly proposed method in this paper. As shown in Figure 4, the RAIM FDE will be used after calculating the simulated pseudorange of a candidate. It is interesting to note the idea of the pseudorange difference of each candidate in the proposed 3D map positioning method is similar to the pseudorange residual of the RAIM algorithm. In the proposed method, the pseudorange difference is defined as the pseudorange measurement minus the simulated pseudorange. The simulated pseudorange is calculated as:(1)ρ^n(i)=Rn(i)+c(δtr(i)−δtnsv)+In+Tn+εnrefl(i)where n denotes the index of the satellite, i denotes the index of a position candidate (particle), denotes geometric distance between the satellite n and the candidate i, c denotes the speed of light, the satellite clock and orbit offset are corrected using the satellite broadcast model. The ionospheric delay I and the tropospheric delay T are obtained from the Klobuchar and Saastamoinen models, respectively. The reflection delay is estimated by the ray tracing and city building models [23,24,25]. The receiver clock offset, , for the candidate is modified to minimize the difference between the simulated set and the measured set. If an abnormal signal is used in the calculation of the receiver clock bias minimization, the optimized receiver clock bias will be inaccurate. The flowchart of the RAIM multiple fault exclusion in the proposed method is shown in Figure 5.

Bottom Line: The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange.Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal.According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. qmohsu@kmj.iis.u-tokyo.ac.jp.

ABSTRACT
Currently, global navigation satellite system (GNSS) receivers can provide accurate and reliable positioning service in open-field areas. However, their performance in the downtown areas of cities is still affected by the multipath and none-line-of-sight (NLOS) receptions. This paper proposes a new positioning method using 3D building models and the receiver autonomous integrity monitoring (RAIM) satellite selection method to achieve satisfactory positioning performance in urban area. The 3D building model uses a ray-tracing technique to simulate the line-of-sight (LOS) and NLOS signal travel distance, which is well-known as pseudorange, between the satellite and receiver. The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange. The measurement of the satellite will be excluded if the simulated and raw pseudoranges are inconsistent. Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal. According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

No MeSH data available.